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Full text of "Ascorbic acid content of selected vegetables during stages of preparation and service at a college cafeteria"

THE ASCORBIC ACID CONTENT 

OP SELECTED VEGETABLES DURING STAGES 

0? PREPARATION AM SERVICE AT A COLLEGE CAFETERIA 



by 
SISTER FRANCIS HUGH ffALEKB, 0. S. U. 
B. S. f Marymount College, 1933 



A THESIS 

submitted In partial fulfillment of the 
requirements for the degree of 

MASTER OF SCIENCE 

Department of Food Economics and Nutrition 

KANSAS STATE COLLEGE 
OF AGRICULTURE AND APPLIED SCIENCE 

1946 



11 



I Alia03 674170 

TABLE OP CONTESTS 

INTRODUCTION 1 

REVIEW OP LITERATURE 3 

Tomatoes 4 

Cabbage 7 

Potatoes 12 

Spinach 21 

SAMPLING PROCEDURE 26 

Tomatoes 27 

Cabbage 28 

Potatoes 30 

Spinach 32 

CHEMICAL PROCEDURE 33 

DISCUSSION OP RESULTS 36 

Tomatoes 36 

Cabbage 38 

Potatoes 40 

Spinach 41 

SUMMARY 44 

ACKNOWLEDGMENT 46 

LITERATURE CITED 47 

APPENDIX 52 



INTRODUCTION 

Within recent years the increase in mass feeding has been 
phenomenal. Institutional, commercial, and industrial con- 
cerns as well as our Army and Navy have been the users of 
large quantities of the nation's food supply. Numerous inves- 
tigations are being made to ascertain the quality of food 
served by the various types of eating establishments. The chal- 
lenge that must be met by these establishments to a greater or 
lesser extent is that of offering "short orders," of providing 
some choice of selection, and of giving satisfactory service 
involving quantity preparation. 

Some of the culinary practices that prevail in large 
quantity cooking undoubtedly cause much destruction of certain 
nutritive values in food. Moreover, there Is no reason to 
assume that the price the consumer pays for his food is an 
index of the nutritive value of his diet, whether he chooses 
his meals from expensive hotel dining rooms, coffee shops, 
cafeterias, or from the lowest class restaurants. 

The effect of preliminary preparation and methods of cook- 
ing upon the nutritional value of foods has long been recog- 
nized. In order to encourage the use of the best methods in 
the preparation of foods for institutional service, it Is nec- 
essary to know what standards should be set up. Since there 
is essentially a vast difference between the problems found in 
cooking in the home and in the commercial or industrial food 
unit, many Investigations are needed on the nutritive values 



of food as they are prepared for large quantity serving. 
Recently some studies on Institutional service have been made. 
The results that have been reported have Intensified the Inter- 
est of those who are responsible for large group feeding. 

The purpose of this thesis was to moke a study on an 
Investigation carried out on selected vegetables In the cafe- 
teria at Kansas State College where it was felt that In most 
Instances the practices commonly used In Its kitchen prepara- 
tion and counter service were very oomnendable. For example, 
the use of a staggered time schedule would be expected to be 
effective In conserving the nutritional values of foods. Cook- 
ing vegetables In small quantities made It possible to hare 
freshly cooked ones ready for serving as soon as the limited 
supply previously taken to the counter had been depleted. 
Suoh a plan eliminated the necessity of keeping some of the 
cooked foods warm for an extended length of time on the stove 
or steam table or In a bain marie. Also, a great deal of the 
cooking was done In a pressure steamer, and the cooking peri- 
ods of vegetables were not prolonged. Moreover, this cafete- 
ria featured dishes using uncooked vegetables on the steam 
table. There were other details of procedure that appeared to 
contribute to the conservation of food values. 

These were some of the reasons for choosing to ::take an 
Investigation of the effects of certain preparations and 
serving techniques on the ascorbic acid content of selected 
vegetables at the college cafeteria. 

That difficulties would be encountered In carrying out 



this study ware recognized from the beginning. A cafeteria 
kitchen does not readily lend Itself to scientific laboratory 
experiments. Many variable factors have to be brought under 
control In order to draw conclusions from data collected. 
This Is especially true In the case of ascorbic acid studies. 
However, In this work the student was so directed that she 
could discover for herself the numerous problems Involved. 

It Is hoped that further value con be derived from this 
Investigation by maklne many applications of the Information 
gained to the problems of the food service In her own Insti- 
tution. 

REVIEW OP LITERATURE 

Determinations of the ascorbic acid content of the vari- 
ous foods known to be the best and most common sources of this 
vitamin have resulted in the accumulation of data that vary to 
a remarkable extent. Sherman (194G) stated that a table of 
single average figures would be unduly tentative and that in 
most oases a rtnge of the values "within which it is reason- 
able to expect that the mean values when settled will be 
found" should have muoh more meaning. 

There are many reasons to which the differences of the 
original ascorbic acid content of fresh raw foods have been 
attributed. Some of these are the horticultural selection 
of seed, variety, locality, climate, soil, fertilizer, sea- 
son, exposure to rainfall and sunshine, stage of maturity, 
parts of the plant tested, conditions of harvest, handling, 



storage, and methods of transportation. Many studies have 
increased our knowledge of the importance of these factors 
but further investigation is needed. 

Tomatoes 

Somers, Hamner, and Nelson (1945) in order to determine 
some of the factors that might affect the ascorbic acid con- 
tent of tomatoes received at a cannery made a correlated 
study of the several factors operating in a specific location. 
They found that a certain uniform manner of processing toma- 
toes did not result in marked changes of ascorbic acid values. 
Therefore, the variation of the ascorbic acid content of can- 
ned tomatoes must have been due to two sources: differences 
in the ascorbic acid content of tomatoes in the field and 
losses subsequent to picking and processing. These investi- 
gators verified the findings of Hamner, Bernstein, and Maynard 
(1945) who reported that the greatest influence of environ- 
mental variables on the ascorbic acid content of tomatoes was 
that due to variations in light Intensity two weeks previous 
to harvest. Probably fluctuations hitherto attributed to 
location or season at which tomatoes were produced were due 
to the differences in amount of sunshine. 

Wide differences in ascorbic acid content of tomatoes 
have been found to occur within single varieties. Hallswork 
and Lewis (1944) found a range of 24 to 51 mg. per 100 grams 
in the same variety grown in the same plot. 

Intervarietal differences would be expected to cause even 



greater fluctuations. Currenoe (1940) showed that varietal 
differences In the ascorbic add content of tomatoes were 
difficult to demonstrate statistically. Reynard and Kanapaux 
(1942) concluded from several reviews of literature that most 
commercial varieties of tomatoes ranged from about 15 to 40 ng, 
of ascorbic acid per 100 grams of fresh weight. However, 
caution should be used in reoommending any one variety because 
of variations to be expected under the wide range of condi- 
tions where it might be grown. Of edible varieties tosted by 
Reynard and Kanapaux, a small-fruited species gave an ascorblo 
acid range of 35.3 to 72.6 mg. per 100 grams. Thirty commer- 
cial varieties ranged from 11.2 to 21. C mg. per 100 grams. 
Currence (1940) stated that emphasizing varietal differences 
to the grower might be misleading since the variety recom- 
mended as being of high vitamin C content might prove to be 
low under some conditions. Murphy (1942) pointed out that 
although variations within variety caused by geographical situ- 
ation were comparatively large, this should not lessen the 
importance of varietal values. She stated that tomatoes may 
be rendered useless as a source of vitamin C if a variety of 
low ascorbic acid content Is subjected to adverse environ- 
mental Influences. Contrariwise, a high vitamin variety sub- 
jected to the same unfavorable conditions could still contri- 
bute materially to vitamin C requirements. 

Brown and Mosor (1941) found that an 18-day storage per- 
iod of tomatoes either at laboratory temperature or In the 
refrigerator at 6.6° C. resulted in complete retention of 
their asoorblo acid. However, Somers et al. (1945) suggested 



that holding tomatoes more than a day, if they were Injured 
and In a poor condition, might affect their ascorbic acid 
retention considerably. 

The rate of destruction of ascorbic acid during cooking 
varies greatly with different foods. Since this vitamin is 
not autoxidlzable in an acid solution, and since tomatoes are 
not ordinarily subjected to much manipulation a great loss of 
ascorbic acid during cooking would not be expected. Much work 
has been done to determine the effect of cooking upon the as- 
corbic acid retention in some vegetables. Apparently few, if 
any studies, have been made on the effect of cooking raw toma- 
toes. This may be due to the fact that fresh tomatoes are 
usually served raw and that when cooked tomatoes are wanted, 
the canned ones are used. Such seems to be the case especially 
in institutions. 

Daum, Aimone, and Holllster (1943) reported the results 
of a study on the ascorbic acid retentions in institutional 
food service at University Hospital, Iowa City. Approximately 
1400 persons were served in three groups ; therefore the vege- 
tables were necessarily prepared in large quantities. The as- 
corbic acid retention in canned tomatoes cooked for a period 
of thirty minutes was 94.5 per cent. Holding the cooked, can- 
ned tomatoes fifteen minutes on the steam table did not lessen 
their ascorbic acid value. Cooking for thirty minutes and 
holding for one hour on the steam table gave an 83.4 per cent 
retention of the original ascorbic acid content of the canned 
tomatoes. 

Somewhat different results were found by Hinman, Brush, 



and Halliday (1944) who reported no effect on the retention of 
the original ascorbic acid value of canned tomatoes durin a 
boiling period of thirty minutes and subsequent holding period 
of one and one-half hours on a steam table. 

Gleim et al. (1946) reported that heating canned tomatoes 
by various methods required for quantity preparation caused no 
change in the retention of ascorbic acid when tomatoes were 
heated to serving temperature. Simmering for thirty minutes 
affected the retention slightly, and simmering for three hours 
decreased the retention to 75 per cent. 

Cabbage 

Numerous investigations have been made on the ascorbic 
acid value of cabbage. Murphy (1942) found that environmental 
agencies, e.g., sunlight and rainfall and perhaps temperature, 
had a marked influence on the ascorbic acid content of cabbage. 
Evidence also indicated that the ascorbic acid tended to de- 
crease as the tissues became more fully matured. 

Others have reported wide ranges of ascorbic acid content 
of cabbage due to varietal differences. Gould, Tressler, and 
King (1936) found a range of 26 to 56 mg. per 100 grams in six 
varieties and strains. They found that the same variety did 
not have the same ascorbic acid content at different seasons 
or in different years but that varieties high in ascorbic acid 
yield as compared with other varieties tended to remain so from 
year to year. 

Van Duyne, Chase, and Simpson (1943) reported that the 



storage of cabbage In tightly closed containers for two months 
at a temperature of -0.5° to 4.0° C. gave good ascorbic acid 
retentions. Losses did occur during the third month of stor- 
age and when the stored cabbage was held subsequently at room 
temperature, 19.4° C. for three days. Holding the cabbage for 
a week in the refrigerator at a temperature of 2.0° to 2.5° C. 
did not affect the retention. These findings seemed to corre- 
late with the report of Mayfield and Richardson (1940) who 
observed that a six-months' storage at 7.2° C. and a relative 
humidity of about 55 per cent resulted in approximately 75 per 
cent retention of the ascorbic acid value of cabbage. 

Pyke (1942) performed an experiment to show the compara- 
tive effects of various methods of shredding or mincing cab- 
bage. He demonstrated that the less the injury to the tissue 
oells, the greater the ascorbic acid retention. The use of 
(1) a sharp knife which caused no noticeable bruising or dis- 
coloration in shredding, (2) a household shredder which caused 
more bruising than the above, and (3) a household grater which 
caused considerable bruising and even discoloration of the cab- 
bage gave results in harmony with theoretical considerations. 
In (1) the asoorbic acid content was not lessened. A ninety 
per cent retention was found in (2) and (3) showed a 66 per 
cent retention. The greatest decrease in the ascorbic aoid 
content in (2) and (3) occurred during the first five minutes 
after the cabbage was shredded. After the initial changes, the 
retentions did not vary significantly within a three-hour hold- 
ing period. 

Lampltt et al. (1942) being interested also in finding a 



correlation between mechanical breakage of cells and the reten- 
tion of ascorbic acid, resorted to the expedient of testing the 
liquid pressed out of shredded cabbage. They confirmed the 
results of Pyke that the retention varied with the extent of 
rupture of the cells and that the concentration of ascorbic 
acid fell rapidly during the first ten to 15 minutes. The as- 
corbic acid value remained oonstant for three-hour periods 
when cabbage was held at 15° C. 

Van Duyno, Chase, and Simpson (1943) reported that the 
advance preparation of shredding cabbago and allowing it to 
stand for one hour in air gave an ascorbic acid retention of 
07 t 2 per cent. Allowing the shredded cabbage to stand In 
water for one hour resulted in the retention of 94 ± 1 per cent, 
and that held in water for three hours retained 96 ± 2 per cent. 

MoCay, Pijoan, and Taubken (1944) reported that the use 
of a plastic knife for cutting cabbage caused greater retention 
of ascorbic acid during holding periods of the cabbage than 
did the use of a steel knife or food chopper. 

Qulnn et al. (1946) reported that cabbage that had stood 
at room temperature for 20 minutes did not show a marked dif- 
ference in ascorbic acid oontent whether the cabbage had been 
prepared by shredding or by cutting with a knife. 

Wellington and Tressler (1938) having reviewed various 
reports concerning the ascorbic acid content of oooked cab- 
bage found that great differences had been observed. They 
made a comparison of three methods of cooking— boiling, steam- 
ing, and panning. They concluded that the amount of aaoorblo 



10 



acid extraoted by the cooking water in boillne and in steaming 
varied somewhat according to the more or less finely divided 
oondltlon of the cabbage. About two-thirds of the original 
ascorbic acid was retained in panning, and since there was no 
excess liquid the oabbage itself retained the greatest amount 
of vitamin C when cooked by this method. 

Having made an investigation on the cooking of oabbage 
by boiling, Gould, Tressler, and King (1036) pointed out that 
the length of time required to bring the water to a boll after 
the cabbage whs added seemed to be of significance. They found 
that about 25 per cent of the ascorbic acid was destroyed be- 
fore the cooking water began to boll and that very little was 
lost thereafter, although a considerable amount was dissolved 
In the cooking water. 

Van Duyne, Chase, and Simpson (1943) reporting on the 
effect of various home practloes on the ascorbic acid content 
of oabbage, stated that when cabbage was boiled for seven min- 
utes in the proportions of one part by weight of cabbage to 
one-half, two, and four parts of water the percentage reten- 
tions were, respectively, 70 ±2, SO $ 3, and 51 ± 1. They 
made a study on the effect of boiling cabbage in twice its 
weight of water for different lengths of time. The results 
showed percentage retentions of ascorbic acid as follows: 
after seven minutes, 55 x 2; after 15 minutes, 52 ± 1; after 
25 minutes, 52 t 2. Having compared the effects of cooking 
oabbage to the same degree of "doneness" by boiling (1) oov- 
ered in twice its weight of water for seven minutes, (2) un- 
covered in twice its weight of water for eight and one-half 



11 



minutes, and (3) uncovered In four times Its weight of water 
for five and one-half minutes, they found these percentage 
retentions of ascorbic acid: in (1), 56 ± 2; in (2), 50 ± 2; 
and (3), 49 1 1. 

Ireson and Eheart (1944) reported that using a large 
amount of water, 1200 cc. to 240 grams of cabbage, resulted in 
a 54 per cent retention of ascorbic acid. About 37 per cent 
of the vitamin was extracted in the water and nearly nine per 
cent was oxidized. When a smaller amount of water was used, 
40 cc. to 193.7 grams of cabbage, the 16 per cent loss of as- 
corbic acid was due to oxidation. 

Noble and Waddell (1945) showed that cooking cabbage in 
a tightly covered pan with just enough water to cover, or in a 
steamer, or in a pressure saucepan, retained approximately the 
same proportion of its original ascorbic acid. Cabbage coolced 
in an open kettle with enough water to cover during all of 
the cooking period retained much less than that cooked in the 
steamer or pressure saucepan. In another study reported In 
1946, these same workers found results comparable to those 
Just mentioned. The retention of ascorbic acid in cabbage 
cooked in a steamer and in a pressure saucepan averaged slightly 
less than 70 per cent, whereas that of cabbage cooked by the 
tightly covered pan method retained about 60 per cent and that 
by the open kettle method retained about 35 per cent. 

Higgins (1942) in a comparative study of institution and 
home-cooked vegetables found that cabbage cooked in large 
quantity was comparable in quality and ascorbic acid reten- 
tion to that cooked according to ordinary home procedures. 



12 



Holding over steam for one hour affected the retention of as- 
corbic acid. 

Daura, Almone, and Holllster (1943) reported a study on 
large quantity cookery of cabbage. About 300 pounds of cab- 
bage were usually cooked at one time, but excellent flavor 
and color were retained. The range of ascorbic acid in the 
raw cabbage in 12 determinations was found to be 21.0 to 26.0 .ug. 
per 100 grams. After the cabbage was oooked the range was 12.0 
to 19.0 nig. The percentage retentions of ascorbic acid in 
cabbage in cooking, in holding 15 minutes on the steam table, 
and one hour on the steam table were: 59.1, 54.6, and 45.5 
per cent respectively. 

Potatoes 

Although extensive research has been carried out on pota- 
toes, it is difficult to conclude to what extent they enrioh 
the vitamin C content of our diet. The various factors which 
influence the ascorbic acid value of potatoes have been inves- 
tigated by many scientists. In some cases the work is being 
continued. 

Leichsenring (1944) made a compilation of data from the 
agricultural experiment stations of Illinois, Nebraska, North 
Dakota, and Minnesota. In reporting the studies made on 
variety, she stated that marked varietal differences in the 
ascorbic acid content of potatoes were found. The highest 
and lowest values attributed to variety showed a difference 
of 113 per cent. It was indicated thtt some varieties having 



13 



comparatively higher ascorbic acid values tended to have 
approximately the sumo values from year to year. 

Dove, Kurphy, and Akeloy (1943) also reported evidenoe 
showing that potatoes of higher ascorbic acid value could prob- 
ably be counted on to yield similar values from year to year. 

IJdo (1937) found varietal dlfferancea up to 60 per cent 
In the ascorbic acid content of potatoes and not more than a 
ten per cent difference in tubers of the same variety. 

Esselen et al. (1942) in a study on the effect of variety 
found that in many cases differences between varieties were 
less than differences within a singlo variety. They cave 
13.1 nig. per 100 grans as an average yield of Irish Cobblor 
and 9.7 mg. per 100 grams as an average of Chippewa potatoes. 
These figures were based on the results of tests niado on pota- 
toes from several statou. 

Leichsanring (1944) said that although locality appeared 
to be a factor of sorao importance In the ascorbic acid content 
of potatoes, maturity and season seemed to be cor.conitant fac- 
tors . Her data showed that the same varieties of potatoes 
harvested during October, 1943, In Nebraska and North Dakota 
had higher ascorbic acid values than those harvested in Minne- 
sota during October, 1942. In these reports the Irish Cob- 
bler variety was consistently the highest. Its ascorbic acid 
values were these: In North Dakota, 27.1 mg. per 100 grams; 
in two different places in Nebraska, 23. S mg. and 33.2 mg.; 
and at three plaoes in Minnesota, 12.6, 16.4, and 19.0 mg. 

Esselen et al. (1942), having made a study on potatoes 



14 



Immediately after they were dug at their own station in Massa- 
chusetts and on those shipped "soon after harvest" from Cali- 
fornia, Kentucky* Maine, and Hew York, did not attribute very 
great importance to the effect of different geographical areas* 

According to Leichsenrlng (1044) the investigations car- 
ried out by the Nebraska station on five varieties of potatoes 
showed marked and continuous decrease during the growing per- 
iod as well as after harvesting and during storage. An ascor- 
bic aoid content of 36,8 mg, per 100 grama of immature Irish 
Cobbler potatoes was found on June 30, 1043. Weekly analyses 
thereafter shov ed continuous decreases in ascorbic aoid con- 
tent. At the time of harvest on August 10, 1943, a value of 
23.8 ng. per 100 grems was found. 

Reports concerning the distribution of ascorbic acid in 
the potato tuber vary somewhat. Rolf (1940) found that the 
concentration of ascorbic aoid was higher In the bud end than 
in the stem end. Immature potatoes of the Chippewa variety 
showed practically no difference in the distribution of ascor- 
bic acid in the various sections of the tubers, although there 
was. a slight tendency toward higher concentration In the bud 
end as they reaohed maturity. New Green Mountain potatoes 
bought on the market showed only a slight tendency to have a 
higher aaoorbic acid content in the bud end than in tho stem 
end when purchased. This difference became very apparent by 
the end of a week and increasingly more pronounood thereafter. 
The Leiohsenring data (1944) seemod to indicate that the as- 
corbic aoid content of potatoes was greater at the apioal end 



15 



then at the stem end of the tuber* 

IJdo (1938) reported that there was a uniform distribu- 
tion of ascorbic acid throughout the potato, but Julen (1944) 
found that the concentration of vitamin C was greater in the 
layer nearest the peel than in the oore. 

Esselen et al. (1942) found that in raw potatoes there 
was an even distribution of ascorbic acid in the tuber itself 
with a lesser amount in the skin. However, in boiled potatoes 
there was a greater amount of aacorbio acid in the area be- 
tween the central and epidermal portions. The skin and part 
just beneath it were about equal in ascorbic acid content. 
In baked potatoes the greatest concentration of ascorbic acid 
was in the central portion with the amount decreasing pro- 
gressively toward the skin. These workers concluded that some- 
thing happened during cooking to change the distribution of 
ascorbic acid in potatoes. They suggested that this effect 
might be due to the higher temperature maintained in the 
outer portions because of direct contact with the heating 
medium. In the case of boiling some of the vitamin was leached 
into the water. Rolf (1940) reported that she found a similar 
distribution in cooked and uncooked potatoes; therefore there 
was but little diffusion of the vitamin during cooking. 

According to Leiohsenring (1944) the Minnesota station 
found that the size of the tuber was not a significant factor 
in the ascorbic acid content of potatoes. Esselen et al. (1942) 
also reported that there was no correlation between the size 
of tubers and their asoorbio acid content. They found marked 



16 



variations In both small and large nature ran potatoes. 

Rolf (1040) pointed out that although a range of 1.5 mg, 
to 53.0 mg. of ascorbic acid per 100 grams of potatoes had boon 
reported by various workers, their investigations showed that 
newly harvested potatoos were highest in ascorbic acid and that 
this quantity diminished very rapidly during the first part of 
storago and more gradually later. She stated that storage at 
25.5° C. of immature Chippewa potatoes resulted in an 80 per 
cent retention of ascorbic acid after one week and C4 per cent 
after three weeks. Hew Green Mountain potatoes bought on the 
market showed a retention of 86 per cent in about ten days at 
25.5° C. She found that the ascorbic aoid value of three vari- 
eties of potatoes stored at 15.5° C. decreased rapidly during 
the first few weeks and then more gradually until at the end 
of 26 weeks, the ascorbic aoid had nearly reached a plateau 
value. A storage temperature of 4.5° C. caused a greater de- 
crease. The Oreen Mountain variety stored at 15,5° C. lost 
50 per cent in five months. This worker stated, hovvever, that 
evidence seemed to lndioate that the detrimental effects of 
storage at low temperature upon the asoorbic aoid content of 
potatoes might be offset to some extent by later storage at a 
higher temperature. 

All the station reports summarized by Leichsenring (1044) 
indicated that during the storage of potatoes their asoorbic 
aoid retentions were gradually and significantly decreased. 
A storage temperature of 10,0° C. seemed to be more favorable 
for ascorbio acid retention than 4.4° C. In Nebraska Triumph 



17 



potatoes harvested in August and stored at 10,0° 0. shoved 
ascorbic acid values of 16.5 mg. per 100 grass in Deoember and 
7.9 mg. in April. Those stored at 4.4° C. had an ascorbic 
add value of 5.3 qg« in Deoember and 5.2 rag. in April. 

Other studies on the effeot of temperature and length of 
storage correlate rather closely with the data given above. 
Esselen et al. (1042) observing the effect of storage repor- 
ted that two varieties held five months at 2.2° C, approxi- 
mately the temperature of oold storage, had a higher asoorbic 
acid value than the same varieties held at 4.4° to 10.0° C, 
similar to the temperature of dry 'underground storage? but 
four varieties hud greater ascorbic acid value after being 
stored for five months at the higher temperature. Storage 
seemed to level off the differences between varieties in ascor- 
bic acid content. 

At the University of Wyoming Agrioulturo Experiment Sta- 
tion (1040-1941) it was found that the ascorbic acid retention 
in potatoes ranged from 43 to 60 per cent during the four- 
month storage period between Deoember and May. The temperature 
of the storage was not given. 

Julen (1944) of Sweden reported that potatoes stored 
Indoors at 18,0° to 20,0° C. retained more vitamin C than 
those stored at 2,0° to 3.0° C. 

Lelohsenring (1944) noted that the differences in the 
asoorbic add retentions of potatoes during cooking were attri- 
butable to suoh factors as amount of water used, sire of potato 
pieces, length of cooking time, method of cooking, and manner 



18 



of sampling. The Illinois station reported the following per- 
centage retentions of ascorbic acid in potatoes during cooking: 
after baking, 87; boiling in skins, 103; peeling and steaming, 
86; peeling and boiling, 85; peeling, halving, and cooking in 
the pressure cooker, 85. Work at the Nebraska station showed 
that allowing cooked potatoes to stand for 15 minutes before 
analysis decreased the retention of ascorbic acid. 

Rolf (1940) found that the boiling and steaming of unpared 
potatoes were the cooking methods least destructive of vitamin C. 
Baking and pressure cooking caused slightly decreased retentions 
while boiling pared potatoes affected the retention to a greater 
extent. The ascorbic acid retention In any of these methods 
was not less than 75 per cent. 

Esselen et al. (1942) found that in eight varieties of 
potatoes there was a smaller average retention of ascorbic 
acid in baking than in boiling the whole potatoes in the skin. 
These workers made the observation that the addition of one 
per cent UaCl to the cooking water of potatoes seemed to aid 
in the retention of ascorbic acid. They reported that boiling 
In the skin, baking and French frying appeared to be the beat 
methods of cooking potatoes from the standpoint of ascorbic 
acid retention. The percentage retentions after cooking by 
various methods ranged from 20 to 67. The procedures of peel- 
ing, cutting in half, and slicing of raw potatoes, and the 
mashing of potatoes, in the order named, caused increasing 
losses of ascorbic acid. Potatoes boiled and then fried re- 
tained 21 per cent of their original ascorbic acid value. 

At the University of Wyoming Agricultural Experiment 



19 



Station it was reported that one-third of the ascorbic acid 
of potatoes wus extracted by the water in which they were 
boiled. 

Richardson and Mayfield (1943) found that boilinc unpared 
potatoes caused no significant effect on their ascorbic acid 
retention. Cut, pared potatoes retained approximately 01 per 
oent after boiling. They reported that cooking pared potatoes 
in a pressure saucepan under steam pressure of 15 pounds gave 
better retention of ascorbic add than did boiling in an ordi- 
nary kettle. 

Recently there have been studies on the ascorblo acid 
content of potatoes as affected by Institutional methods of 
preparation and service. 

Higgins (1942) found that the retention of ascorbic acid 
of potatoes cooked by Institutional methods was slgnifioantly 
less than of those cooked by home methods. 

Kahn and Halliday (1944) reported a study on the vitamin 
values in foods prepared in institutional quantities. Steam- 
ing in tho skin was the only method of preparation which did 
not affect the retention of aBOorblc acid in potatoes. Hew 
potatoes, steamed in the skin, oan take the place of a citrus 
fruit as a source of ascorbic acid. French-frlod potatoes 
showed good retentions of asoorblo acid when the temperature 
of the frying fat was kept oonstant. Baked potatoes retained 
80 per cent of their asoorbio acid during baking. The reten- 
tion was decreased to 50 per cent after a 43-mlnute holding 
period on the steam table. A 61 per cent retention of the 



20 



ascorbic acid value was found as the rosult of cooking and 
mashing potatoes. The average retention of the noshed pota- 
toes after being held for 75 minutes was five per cent of the 
original value. 

Daum, Airaone, and Holllster (1943) reported that both 
new and old potatoes showed slightly decreased values of ascor- 
bic acid after cooking. A 15-mlnute holding period affected 
the retention and holding one hour greatly decreased the re- 
tention* 

Stroightoff et al. (1946) undertook a study to determine 
the effeot on the ascorbic acid content of potatoes of large- 
scale methods of preparation such as those practiced in the 
army consolidated mess and company raess. They reported evi- 
dence to show that holding peeled raw potatoes covered with 
water in a refrigerator overnight, or as long as 22 hours, or 
in running water for four hours, did not groatly affect the 
retention of ascorbic acid. This la a point of significance 
because holding potatoes In water is a practice frequently 
resorted to, eapoclally In Institutions, Richardson and Kay- 
field (1943) found that the presoaklng of pared potatoes In 
water for four hours decreased the subsequent retention of 
aaoorbio acid in boiling or pressure cooking by about four 
per cent. Soaking for four hours in 2.5 per cent salt solu- 
tion before cooking resulted in better retention of vitamin C 
than ocourred when potatoes were cooked at onco after prepara- 
tion. 

Strelghtoff et al. (1946) found that cooking potatoes In 
the pressure steamer wus most conservative of the aaoorbio 



21 



acid value. The retention In this case was about 04 per cent. 
Baking In tne Jackets a minimum length of time and boiling 
gave percentage retentions of 88 and 87. When steamed pota- 
toes were mashed, there was very little retention of ascorbic 
acid. 

Jenkins (1943) reported that cooked whole potatoes held 
at room temperature retained more ascorbic acid than mashed 
potatoes. Whether the potatoes were kept hot in small por- 
tions or large quantities did not seem to affect the retention. 
Keeping mashed potatoes warm for one hour gave a 25 per cent 
retention of ascorbic acid. The length of time consumed in 
the mashing of potatoes was a factor In ascorbic acid retention. 

Spinach 

Cutlar et al. (1944) in making a review of literature 
reported various ascorbic acid values for spinach. The amounts 
ranged from 19.8 to 123.9 mg. per 100 grams. Tressler, Mack, 
and King (1936) found that variety was an Important factor in 
the ascorbic acid content of spinach. Broad Flanders yielded 
an ascorbic acid value of 89.0 mg. per 100 grams and Princess 
Juliana had the lowest value, 38.0 mg. per 100 grams. They 
also reported that soil and growing conditions exerted a def- 
inite influence on the ascorbic acid content of spinach. 
Twelve varieties of spinach grown on upland clay loam soil 
averaged 50 per cent higher than those grown on muck soil. 
Spinach grown in the autumn had higher ascorbic acid values 
than that grown in the spring. Isgur and Fellers (1938) in 



22 



a study on the effeot of fertilizer on Sew Zealand spinach 
found that high nitrogen treatments did not increase the as- 
corbic acid value. 

Slepykh (1940) reported thct the ascorbic acid of the 
spinach leaf reached its maximum content during the middle 
stage of development and decreased with the maturity of the 
plant. Sheets et al. (1941) found that the ascorbic acid 
value of splnaoh was more concentrated in the leaf blades than 
in the petioles. Trossler, Hack, and Xing (1936) gave data 
to show that the ascorbic acid in splnaoh is principally in 
the leaves and that the stems are almost devoid of this vitamin. 

Tresaler, Mack, and King (1936) reported that splnaoh 
stored for three days at 1.0° to 3.0° C. retained nearly all 
its vitamin C, but that held at room temperature lost approxi- 
mately one-half its ascorbic add value in three days and 
almost all in seven days. Wheeler and Tressler (1939) found 
that freshly harvested New Zealand spinach had an ascorbic 
acid content of 44.0 mg. per 100 grams. After storage at 
room temperature for four days the value decreased to 21 mg. 
and storage of the fresh spinach for two weeks at 1.0° to 
3.0° C. decreased the value to 16.0 mg. per 100 grams. Ran- 
ganathan (1936) tested the effect of storage at room tempera- 
ture on samples of fresh spinach collected during dry weather 
and of spinach collected during wet weather. The initial 
ascorbic acid oontents were 36.9 and 53.3 rag. per 100 grams, 
respectively. After 24 hours the percentage retention of 
ascorbic acid in the dry weather splnaoh was 70.0 and after 
192 hours, 21.7. The wet weather spinach showed retentions 



25 



of 87.1 and 59.3 per cent, respectively, for the two storage 
periods. 

Procter and Greenlie (1930) reported that oven for short- 
time storage of spinach, temperatures below 4.4° C, tended to 
conserve vitamin C which deteriorated rapidly at ordinary room 
temperatures, '/epplin and Elvehjen (1944) tested spinaoh soon 
after harvesting that had a high original ascorbic acid oontent 
of 79 to 90 rag. per 100 grams. The retention decreased rapidly 
during storage at room temperature for 24 to 48 hours but was 
more stable thereafter. Refrigerator storage offered acme 
protection and after 72 hours the retention was slightly more 
than 50 per oent. When spinaoh was exposed to room tempera- 
ture again, the oxidation proceeded at a high rate. 

Platenius and Jones (1944) said that spinaoh held in an 
atmosphere of low oxygen oontent retained more than three 
times as muoh asoorbio acid as the lots in normal air. The 
presence of 18 per oent CO2 at a temperature of 66.0° F. 
accelerated the destruction of ascorbic acid but 5.3 per oent 
CO2 at 50.0° P. slightly retarded the loss of asoorbic acid. 

Halliday and Eoble (1936) having made a comparison of 
the asoorbio aoid retention during oooklng of a number of 
vegetables, found that spinaoh retained the least amount, 24 
per oent, during boiling for eight to nine minutes in a large 
amount of water, i.e., 2f C. to 370 grams of spinaoh. Of the 
76 per oent loss, 47 per cent was totally destroyed and 29 per 
cent was dissolved in the oooklng water. When cooked in only 
the water clinging to the leaves, approximately 36 per cent 



24 



was retained. Of the amount lost about 45 per cent was des- 
troyed and 19 per cent was dissolved in the cooking water. 
Dunker and Fellers (1930) made a study on the effect of the 
amount of water used in oooking spinach. The retention of 
ascorbic acid in spinach decreased as the volume of cooking 
water increased. The solid portion retained a range of 32 to 
67 per cent depending on the amount of water used. One pound 
of spinach steamed with 100 cc, of water retained about 68 per 
cent. One pound of spinach cooked with 450 cc. of water re- 
tained about 33 per cent. Ten to 15 per cent of the ascorbio 
acid was leached out into the liquid during steaming and dur- 
ing cooking with the larger amount of water. 

Phillips, Dickorson, and Penton (date of the report was 
not given) found that cooking 600 grans of spinach with no 
more water than that which clung to the leaves gave an ascor- 
bic acid retention of 60 per cent. The oooking time required 
was 12 minutos. Cooking the same amount of splnaoh In 250 
grams of water and in 626 grams of water for six minutes gave 
retentions of 55 and 41 per cent respectively. They found 
that oooking 600 grams of spinach in 625 grams of water at an 
initial temperature of 90,5° C, gave a 41 per cent retention 
of ascorbic acid. The sane amount of spinach in the same 
amount of water at an initial temperature of 20.0° C. gave a 
34 per cent retention. The cooking times required were six 
minutes when the initial temperature was higher and 15 minutes 
when it was lover. 

Cutlar et al. (1944) reported that in quantity oooking 



25 



the retention of the ascorbic acid of spinach was increased 
by ten percent when the amount of water was Increased four 
times above the amount required to cover the spinach as it 
began to cook In steam- jacketed kettles. Spinach, in 15- 
pound lots, boiled In otoam-Jackoted kettles with eight quarts 
of water retainod 50 per oont of tho original asoorbio acid 
but only 40 per cent when four times as much water was used. 
The same amounts of splnaoh cooked in a container on tcp of 
the range with eight quarts and two quarts of water retained, 
respectively, 32 and 33 per cent of the ascorbic acid. These 
workers observed that when the smaller amount of water was 
used, more time was required for the spinach to reach a stage 
of "doneness" than that cooked in the larger amount of water. 
The length of time required for the water to reach the boiling 
point after the spinach was added depended on the amount of 
water and the concentration of heat on the bottom and sides 
of the cooking utensil. Increasing the quantities of spinach 
cooked at one time decreased the ascorbic acid content. Spin- 
ach in five-pound lots cooked in the pressure steamer, stecaa- 
Jccketed kettle, and In a stockpot on the range had decreasing 
amounts of ascorbic acid according to the order of equipment 
named. The retentions for the pressure steamer were 76 per 
cent; for the steam-Jacketed kettle, 67 per cent; and for the 
stockpot on the range, 53 per oent. Splnaoh In 15-pound lots 
cooked in a 25-gallon steam-Jacketed kettle gave a retention 
of 50 per cent. The same amount cooked in the same amount of 
water in a 16-gallon stockpot on the r ange gave a retention of 



26 



32 per cent. 

Cutlar at al. (1944) also i'ound that drained cooked 
spinach held at 150° P. in a heated food service unit retained 
85 per cent of its ascorbic acid after 15 minutes, 61 par cent 
aftor 30 minutes, and 25 per cent after 120 minutes. 

SAMPLIIIO PROCEDURE 

Since the purpose of this study was to make comparative 
determinations of the ascorbic acid content of selected vege- 
tables during stages of preparation and service, it was found 
advisable to take samples as representative as possible from 
the lots of vegetables as they were ordinarily prepared by the 
regular workers of the cafeteria. Thus no effort was made to 
determine the highest possible original content in any case. 
Samples were also tested to determine the effects of 15-ralnuto 
holding periods on the stean table because during ordinary 
serving periods 15 minutes was the longest time any food was 
held on the steam table before it was served and the dish 
replenished by a new supply from the kitchen. At the cafeteria 
all the samples of the vegetables to be tested were collected 
into previously prepared bottles of metaphosphoric acid, taken 
to the laboratory, and there analyzed at once for their ascor- 
bic acid content. 

In order to become familar with kitchen procedures and 
details of the problems involved in this study, small numbers 
of samples were taken over a period of several days, first of 
tomatoes and then of cabbage. Later a larger group of samples 



27 



of each of the vegetables were taken for more extensive study. 

Tomatoes 

At the cafeteria work was usually started on tomatoes 
about 10:30 a.m. when they were taken from the refrigerator, 
weighed, washed, oored and quartered. Then they were sent to 
the kitchen. 

For sampling, tomatoes were selected that were free from 
blemish and of uniform ripeness as Indicated by color and 
firmness. For the analyses of raw tomatoes each of four washed, 
cored tomatoes was cut into quarters. One quarter of each of 
the tomatoes was put into each of four bottles of acid. For 
analyses of cooked tomatoes, a whole raw tomato, washed and cored, 
was weighed and put into each of six individual baking 
dishes. The small porcelain dishes were used in order to keep 
the weighed tomatoes separate. These dishes of tomatoes were 
placed in a shallow stainless steel pan, covered with a damp 
cloth and held at kitchen temperature until the tomatoes to 
be served on the steam table were cooked. Then three of the 
dishes were plt.ced in the steamer or oven at the same time and 
for the same length of time as were the tomatoes to be served 
first. The remaining three dishes were held for a longer 
period at kitchen temperature and then cooked as above. After 
the samples were cooked, they were transferred into bottles 
of acid. Approximately 50 samples of tomatoes were thus stud- 
ied over a period of five days. 

For a larger number of samples, four tomatoes were cut 



28 



into fifths. One-fifth was placed into each of five bottles 
of acid which had been previously weighed. Another four toma- 
toes were cut into fifths and put into each of five baking 
dishes and the procedure was repeated using bottles or baking 
dishes until the following samples were collected: ten for 
testing tomatoes raw, ten for testing tomatoes after they had 
been steamed for five minutes, and ten for testing tomatoes 
steamed five minutes and held on the ste ■ m table for 15 minutes. 

Cabbage 

Over a period of five days 39 samples of cabbage were 
analyzed for their ascorbic ucid content. The preliminary work 
on the cabbage was usually begun about 10:00 a.m. in a basement 
room of the cafeteria and oontlnued until the cabbage was ready 
for cooking. Approximately 15 pounds of cabbage were cleaned, 
washed, quartered, cored and sent to the kitchen where the 
cabbage was shredded on an electric Hobart slicer. The shred- 
ded cabbage was put into a large stainless steel pan 20" x 19° 
x 4", covered with a well dampened cloth and allowed to stand 
until it was ccoked. Generally there was a standing period of 
30 to 45 minutes in the kitchen before the cabbage to be served 
first on the counter was placed in the steamer. 

In order to ;et random sampling, the cabbage as soon as 
it was shredded, was well mixed with forks, and samples were 
taken for chemical analysis. Approximately two-ounce portions 
were weighed and put into each of three bottles of acid which 
had been prepared for this purpose. In all instances great 



29 



oare was taken to have the samples well oovered with aold. 
lasaediately preparation for taking samples of cabbage for 
steaming was begun. About one pound of shredded cabbage was 
plaoed in a small stainless steel pan. Fifty-gran portions 
were welgnad Into each of six porcelain baking dishes which 
were placed in a large shallow stainless steel pan, covered 
with • damp oloth and allowed to remain in the kitchen until 
the cabbage that was to be served first on the counter was 
cooked. This cabbage for serving on the counter Hsi the sam- 
ples for testing for ascorbic acid content were plaoed in the 
steamer at the same time and for the some length cf time. 
When the cabbage was taken from the steamer, three of the sam- 
ples were put into aold. Three of the oabbage samples, as 
soon as they htd been removed from the steamer, were placed 
on the steam table for IS minutes during a regular serving 
period when the steam was turned on as usual, and then collected 
into 6.cid. The baking dishes did not cool rapidly, but It was 
deolded they were the best small containers for this purpose. 
The retention of heat might have been somewhat similar to that 
in a larger quantity of vegetable. 

Samples were also taken from the large quantity of raw 
shredded cabbage after it had stood at kitchen temperature 
for 45 to 60 minutes. 

When a larger number (40) of samples were taken, about 
six pounds of oabbage, cleaned, washed, and shredded, were 
placed in a stainless steel pan. l*rora this three sets of sam- 
ples were taken alternately, i.e., as oabbage was weighed, one 



30 



portion was put into acid, the next portion into a baking dish 
for steaming, and the third portion into a baking dish for 
steaming and holding 15 minutes on the steam table. This was 
repeated until there were ten samples in each lot. After 
being steamed ten samples were collected into acid at once and 
ten were placed on the steam table for 15 minutes. The steam 
table was heated the same as it was during a regular serving 
period. The remainder of the raw cabbage was left in a large 
stainless steel bowl for one hour. It was then mixed with 
forks and ten weighed samples were put Into acid. 

Potatoes 

Exploratory work was done on ten samples of potatoes. 
The samples were taken from the potatoes that were being pre- 
pared for serving on the counter. About 20 pounds of potatoes 
had been washed, peeled in a Hobart machine, eyed by hand, cut 
into quarters, and allowed to stand in water at room tempera- 
ture. Usually the preparation was begun about 8:30 a.m. and 
finished between 9:30 and 10:00 when the potatoes were sent 
to the kitchen. Thus some of the potatoes were in water for 
a longer period of time than others. An attempt was mude to 
take random samples by selecting potatoes from different parts 
of the container. 

Raw potatoes were weighed In 50-gram portions and put into 
four bottles of acid. For samples of cooked potatoes 50 crams 
of raw potatoes were placed In each of four cheesecloth bags 
and Inserted in various parts of the perforated steamer pan 



31 



among the potatoes being prepared for the counter, and steamed 
for 30 minutes. These cooked samples were weighed and put 
Into acid. The average loss of weight was found to bo 1.4 
grams per 50 grama of potatoes. Therofore, It was assumed 
that 48. 6 grams of cooked potatoes were equivalent to 50 grama 
when raw. Accordingly four 4G. 6-gram portions were taken from 
the potatoes mashed in the Hobart mixer after four minutes of 
mashing before the addition of milk. This was not representa- 
tive procedure sinoe the mashed potatoes for serving were 
ordinarily subjeoted to mixing and whipping for a much longer 
time* 

It was decided to uae a dry weight baaia for comparison 
of ascorbic aoid values of potatoes when making observations 
on a largor number (40) of samples. It was felt that this 
method would be more accurate than that of assuming that 1*4 
grams represented the loss in weight per 50 grams of potatoes 
aa was done in the exploratory work. 

For thla aet of samples ten 50-gram portion* of raw pota- 
toes were weighed and put Into aoid. Ten samples taken from 
the lot of potatoes that had been steanod 35 minutes were put 
into acid. Ten samples of the mashed potatoes ready for serv- 
ing were collected into acid. About 600 grama of the mashed 
potatoes for serving were placed in a atalnleas ateel bowl 
and allowed to stand on the baok of the kitchen atove for 45 
minutes. Fifty-gram amounts were put Into each of ten bottles 
of acid. 

For calculating the percentage of dry weight a little more 
than 60 grama of potatoes from each lot from which samplos 



32 



had been taken. I.e., raw, steamed 35 minutes, mashed, mashed 
and held 45 minutes, were put Into wide-mouthed, pint-size, 
Kerr canning Jure which were then tightly sealed and taken to 
the laboratory. Twenty s;rams of each were put Into each of 
three aluminum drying dishes which had been previously prepared 
and weighed. These samples wore dried in a Preas vacuum oven 
at 100° C. and 18 pounds pressure for 18 hours. They were 
weighed and the percentage of dry weight of the various lots 
of potatoes from which they were taken was determined. 

Spinach 

In order to obtain a number of samples of spinach large 
enough to be indicative of results, ten samples were collected 
during various stages of preparation of the spinach. The first 
samples were taken from the spinach as it was delivered, unwashed. 
Fifty-gram portions were weighed and put into acid. The rest 
of the spinach was washed three times and the long stems were 
removed so t hat s»bout one inch of stem was left. The spinach 
was dried by being spread out on tea towels and paper toweling 
and patted dry with paper and cloth towels. It was placed on 
a board and cut with a French knife as was ordinarily done for 
the serving of raw spinach on the steam table. Twenty 50-gram 
portions of this spinach were collected alternately into acid 
and Into baking dishes. The ten baking dishes of spinach were 
held for 15 minutes on the steam table which was heated as for 
ordinary serving, and then the samples were put Into acid. 



33 



The remainder of the raw, washed, and cut spinach was 
held in a large stainless steel bowl at room temperature for 
one hour. Ten 50-gram sanpleB were then put into the acid. 

CHEMICAL nOOBBll 

The indophenol titration method of Bessey and King (1933), 
modified by Mack and Treasler (1937), as described by Bessey 
(1939) was used in analyzing samples for their ascorbic acid 
content. 

To prepare a 0.05 per cent solution of sodium, 2,6-dichlo- 
rophenollndophenol, the indicator or dye used, 125 mg. of 
Indophenol (Eastman) was r j.aced on a filter paper and washed 
into a volumetric flask with hot water. After cooling, the 
volume was made up to 250 cc. The aqueous solution of the dye 
changes slowly ever, at low temperature; hence It was kept in 
the refrigerator and fresh solutions were made not less fre- 
quently than every four dayB. The dye was 3tar.darized against 
ascorbic acid each day it was used. 

The ascorbic acid solution for the standardization of the 
dye wss carefully prepared by dissolving one ampule (0.1 gm. ) 
of crystalline ascorbic acid (Cebione Merck) in three per cent 
metaphosphoric acid and bringing the volume up to 200 cc. 

To standardize the dye, five cc. of ascorbic acid solution 
were diluted with a small amount of distilled water and titrated 
with dye until a very faint pink color persisted for 30 seconds. 

The strength of the ascorbic acid solution was checked by 
titrating a five-cc. portion, to which a arriall amount of sodium 



34 



bioarbonate had been, added, with 0.011? iodine until the end 
point was almost reached. Then two drops of starch solution 
were added to the ascorbic acid solution and titration con- 
tinued by drops until a blue oolor first appeared. The iodine 
solution was prepared by taking 25 cc. of a stock solution of 
approximately 0.2N iodine and making it up to 500 cc. 

A ten cc. portion of 0.01N standard arsenious oxide was 
titrated against the iodine solution in the manner Just des- 
cribed. 

For all standardizations and titrations care was taken to 
have all reagents at room temperature. 

Ascorbic acid is rendered fairly stable in an acid medium 
of proper pH value. Three per cent metaphosphorio acid has 
been found very satisfactory for this purpose. Therefore, the 
vegetables to bo analyzed were oollccted into metaphosphorio 
acid of sufficient concentration to insure a three per cent 
solution after the sample was mixed, and brought up to volume. 
The day before samples were to be taken, 62,5 cc. of 12 per 
cent metaphosphorio acid was put into clear glass bottles with 
unlinod plastic lids. These bottles of acid were weighed, if 
necessary for sample collection, and placed in the refrigerator 
until they were used. 

The samples were oollected at the college cafeteria as 
described in the sampling procedure. 

For the determination of ascorbic acid content, it was 
neoessary to have the cellular structure of plant tissues well 
broken down. For this purpose the Waring blendor was used. 



35 



To prevent excessive frothing, two to three drops of butyl 
■tearate were added to the material before it was ground in 
the blendor. The use of the Waring blendor for cooked pota- 
toes resulted in a nonf llterable starch solution. The use of 
a mortar and pestle for grinding proved satisfactory. Kahn 
and Halllday (1944) reported that samples of cooked potatoes 
macerated in a Waring blendor formed an "opaque gelatinous 
mass." 

After each sample was macerated and thoroughly mixed 
either in the blendor, or in the case of potatoes, with mortar 
and pestle, distilled water was added to the solution to make 
up its volume to 250 co. It was mixed well, filtered, and 
ten cc. aliquot portions were diluted with a small amount of 
distilled water and titrated in duplicate with sodium 
2,6-dlohlorophenollndophenol, A very faint pink whioh faded 
within 30 seconds was considered the end point. Duplicate 
titrations were always made for standardizations and for as- 
corblo acid determinations. Oreater speed and greater preci- 
sion were possible the second time. Prom the sundry titrations 
calculations were made to determine the milligrams of ascorbic 
acid per 100 grams of vegetable. The following formulas were 
used in making the calculations: 
The dye factor or rag. asoorblo acid per co. dye • 

oo. As2 O3 x .00 x cc. lodlno against ascorbic acid 

cc. iodine against Asg O3 x 00. dye against ascorbic acid 

(1 cc, of Il/lOO iodine » .08 mg. ascorbio acid.) 

The mg. ascorbic acid per 100 grams vegetable « 

100 mrc. of vegetable x vol. of sol, x dye faotor x dye titration 
wt. of vegetable used x vol. used for titration 



38 



DISCUSSION OF R2SU118 
Tomatoes 

Experiments carried out on approximately 50 samples of 
tomatoes taken over a period of five days Indicated th.'.t their 
ascorbic acid values varied somewhat and that it was difficult 
to ascribe these fluctuations entirely to any of the various 
steps in preparation. The mean ascorbic acid content In 2£- 
samples of ra?» tomatoes was 17.1 x 1.3 itig. per 100 grama. 
This average corresponds to the lower values in the range of 
15 to 40 mg. per 100 grams of most commercial varieties of 
tomatoes as reported by Reynard and Kanapaux (1S42). It was 
Impossible to find cut where and under what conditions the 
tomatoes used In these experiments had been grown. Storage 
and transportation problems were ^reat because of the war con- 
ditions. It was evident, in so.ue cases, that the tomatoes had 
been picked when very green. Moreover, they were not sorted 
according to s^e, and they *ere not always well packed. The 
fact that the ascorbic acid value of the tomatoes in this 
study was not generally high added Interest to bba project. 
Since tomatoes are usually included among the food3 that con- 
tribute substantially to the vitamin C content of our diet, 
it was of practical value to mates this investigation. 

The range of 14.9 to 20.2 nig. per 100 grams did not show 
as great variation In the raw tomatoes as might have been 
expected because many workers have reported greater ranges 
even in tomatoes of the same variety. In general samples of 
cooked tomatoes seemed to indicate a decrease of tne original 



37 



asoorbic aold content but In the small troupe of samples 
greatly varying results were obtained. In one set of three 
samples there was apparently a 61 per cent retention of the 
original ascorbic acid content when tomatoes were held at 
room temperature after being washed, cored and baked for 22 
minutes. Similar procedures seemed to result in a retention 
of 94 per cent in another set of three samples. In two in- 
stances cooked tomatoes appeared to have a greater asoorbic 
acid content than did the raw tomatoes sampled on the same 
day. These discrepancies oould have been due to the variable 
content of ascorbio acid within the tomatoes. The samples of 
raw tomatoes wore made up of quarters from four different 
tomatoes but for sampling oooked tomatoes, whole tomatoes were 
used. Thus a whole tomato of high original ascorbic acid con- 
tent could have greater value even after being cooked than the 
samples made up of parts of four raw tomatoes if these toma- 
toes happened to be of lower original ascorbic acid content. 
With one exception, the groups of small samples indicated that 
the retention of ascorbio acid was decreased by an increased 
cooking tine. 

Since steaming in the pressure steamer for five minutes 
was the most typical method of oooklng tomatoes at the oafe- 
ter-la, that method of oooklng was the one used in this ex- 
periment when a larger number of samples were taken on the 
same day. Composite samples were taken for testing both raw 
and oooked tomatoes as described in the sampling procedure. 
The mean ascorbic acid values found in the tomatoes were these: 
raw, 16.4 i 0.5; steamed for five minutes, 14.1 t 2.4. Thus 



38 



the retention during cooking was approximately 87 per cent. 
Holding the cooked tomatoes on the steam table for 15 minutes 
caused no further decrease. This latter result Is In accord- 
ance with the report of Gleim et al. (1946) In their study on 
the effect of quantity preparation procedures on canned toma- 
toes. They found that heating the canned tomatoes in a steamer 
for 15 minutes caused "practically no destruction of ascorbic 
acid." 

Cabbage 

Thfi ranr;e of the ascorbic acid content of raw shredded 
cabbage per 100 grama for 25 samples was 35.2 to 54.2 m£. 
Many investigators hove shown that the original ascorbic acid 
content of cabbage may fluctuate greatly. In this study noth- 
ing could be done to control the factors of variety, exposure 
to sunlight during the growing period, and storage of the cab- 
bage previous to purchase. Since the work was done In June 
and the first part of Julv, 1945, summer cabbage was used. 
However, It oould not be determined how much time had elapsed 
since it was harvested, nor at what temperatures it had been 
held. 

An average of 43.5 t 5.9 mg. per 100 "rams found in 25 
samples of raw cabbage indicated a fairly high original ascor- 
bic acid content. 

Shredded cabbage was used for sampling as shreddinr was 
typical of the manner of preparation for serving at the cafe- 
teria and gave an opportunity to have the various parts of the 



39 



oabbage well mixed. Bray and Thorpe (1944) found an asoorbic 
add range of 25 to 79 mg. per 100 grama In ten samples of 
oabbage that had been out Into wedges, then oooked and strained. 
They oonoluded that "ninoed or chopped" oabbage would give 
better agreement between replicate samples. 

Shredded cabbage held at room temperature for one hour 
showed 94 to 96 per oent retentions of the original ascorbio 
acid content of nine samples and 100 per oent retention in 
the group of ten samples. There was only 88 per cent reten- 
tion in one group of three samples. The loss in this case, 
whloh might have been due to finer shredding, was greater 
than the losses reported in the literature by recent workers. 
In these experiments the shredding was done on a Hobart elec- 
tric slloer. Ordinarily the cabbage was cut into shreds about 
three-eighths of an inch wide. 

Six samples of shredded cabbage held for 45 to 60 minutes 
and steamed for seven minutes showed an asoorbic acid reten- 
tion of 79 to 81 per cent of the original value. Ten samples 
steamed for seven minutes Immediately after the cabbage was 
shredded showed an average retention of 68 per cent. 

The retention of ascorbio aoid during holding on the 
steam table for 15 minutes was apparently less when the shred- 
ded oabbage had been held from 45 to 60 minutes before being 
put into the pressure steamer. Six samples of shredded cab- 
bage held for 45 to 60 minutes, steamed seven minutes, and 
held on the steam table for 15 minutes showed ascorbic acid 
retentions of 66 to 74 per cent. Ten samples steamed seven 
minutes and held 15 minutes on the steam table showed an 



40 



average retention of 85 per cent. 



Potatoes 



The potatoes usod In this study were of the Red Triumph 
variety locally produced. Since the work was done about the 
middle of July, it Is probable that the potatoes had been 
recently harvested. The mean ascorbic acid value of 14 raw 
samples 34.2 ± 3.1 rag. per 100 grams, on the basis of wet 
weight, showed that the potatoes had a comparatively high 
original ascorbic acid content. According to the report of 
Leichsenrlng (1944) immature Irish Cobbler potatoes at the 
Nebraska station had an ascorbic acid content of 36.8 mg. per 
100 grams on June 30. The highest value given for Triumph 
potatoes was 29.8 mg. in October. Values were not recorded 
for this variety during June and July in the National Coopera- 
tive Project. The range of 28.3 to 38.2 mg. per 100 grams 
for the 14 samples of raw potatoes was not f-reater than was 
expected because there were some variables that could cause 
such results. The fluctuations could have been due to the 
parts of the tubers tested. The samples were chosen from vari- 
ous portions of the lot of potatoes being prepared for serving. 

The potatoes cooked in a pressure steamer showed a reten- 
tion of approximately 86 per cent. This was comparable to 
some of the results reported in the literature. Mashing the 
potatoes in the manner ordinarily done for serving resulted 
in a retention of 55 per cent of the original ascorbic acid 
content. The calculations made on the dry weight gave almost 



41 



the same results that were obtained on the wet basi3. It was 
noticed thu»t some cooks subjected the mashed potatoes to longer 
periods of mixing and whipping than others. 

Holding the mashed potatoes on the back of the stove for 
45 minutes resulted in an additional loss of ascorbic acid. 
The average ascorbic acid value of potatoes tested immediately 
after mashing was 19.6 t 1.3 mg. per 100 grams (wet basis) and 
that of potatoes, mashed and held on the stove, was 14.7 x 1.1 mg. 

Spinach 

Raw spinach is often served at the college cafeteria. 
The washed, cut, raw spinach is placed in a stainless steel 
bowl. A hot vinegar dressing is poured over the spinach which 
is then held on the steam counter where it is served. 

Since cooking destroys ascorbic acid to a greater or 
lesser extent, there is an advantage in serving some vegetables 
raw. However, the amount of this vitamin retained during the 
preparation of vegetables to be served raw and during their 
holding periods is subject to considerable variation. 

An experiment was made to determine the results of holding 
the cut spinach on the steam table for 15 minutes, and at room 
temperature for one hour. No testa were made on the effect of 
adding the dressing. The vinegar dressing Itself probably did 
not cause a marked destruction of the ascorbic acid content of 
the spinach although adding it when hot might have resulted in 
some decrease. Quinn et al. (1946) found that adding a vinegar 
mayonnaise to shredded oabbage aided the retention of ascorbic 



42 



acid. Similar results might be expected for spinach. 

In this experiment the original ascorbic acid value of 
the spinach was low. Of the first ten samples taken from the 
unwashed, uncut spinach the mean value was 13.0 ± 1.2 mg. per 
100 grama. This was lower than the mean of 15.0 * 2,4 mg. 
found In the ten determinations of the washed, cut spinach. 
The lower values in the unwashed, uncut spinach may have been 
due to the greater quantity of stems which had not been re- 
moved. According to Tressler, Hack, and King (1936) the ascor- 
bic acid content of the stems of spinach is comparatively low. 
The mean ascorbic acid value of the raw, washed, cut samples 
was used for calculating percentage retentions because the 
purpose of this experiment was to determine the effect of hold- 
ing spinach on the steam table for 15 minutes and at roon tem- 
perature for one hour. The variety of spinach and the length 
of time since harvesting could not be determined. However, 
the spinach showed marked deterioration, nearly half of the 
amount purchased, one bushel, had to be discarded as the leaves 
were badly wilted and slimy. According to the literature re- 
ported, variety as well as storage time and temperatures are 
very Important factors in the ascorbic acid content of spinach. 

Holding the out spinach on the steam table for 15 minutes 
gave a mean value of 12.3 i 1.9 mg. per 100 grams for ten sam- 
ples. This was an 82 per cent retention of the original. 
Holding the cut spinach at room temperature, 26.0° C, for one 
hour gave a mean value of 10.8 i 1.7 lag. for ton samples. This 
was a 72 per cent retention of the original and indicated a 



43 



very rnpld destruction. The loss might have bean due to the 
fact that the spinach had been out Into small pieces. The 
loss would probably have been retarded if the spinach had been 
held uncut In the refrigerator and out as needed for serving. 

The results obtained in these experiments carried out on 
tomatoes, cabbage, potatoes, and spinach showed that these 
vegetables as served in the cafeteria at Kansas State College 
contained appreciable amounts of osoorblc acid. By a Judi- 
cious choice of vegetables one could select at this cafeteria 
a day's diet that would contribute an adequate amount of vita- 
min C without including citrus fruit or juice in the menus. 

Sarett et al. (194G) in roporting a study made on the 
vitamin contont of restaurant foods found that "moot of the 
cooked foods contained loss than ten mg. asoorblc acid per 
100 grama" and that the daily ascorbic acid requirements could 
be met only by the inoluslon in the diet of fresh fruit Juices. 

Certainly ascorbio acid is extremely labile and great oare 
should be taken to oonserve the amounts that may be present in 
various vegetables. 



raottsx 

In this study investigations were made to determine the 
effects of oertain preparations and serving techniques on the 
ascorbic acid content of selected vegetables at the cafeteria 
of Kansas State College. 

Experiments were carried out on tomatoes, cabbage, pota- 
toes, and spinach* 

The results indioated that the ascorbic acid oontent of 
tomatoes is somewhat decreased by cooking. Steaming in the 
pressure steamer for five minutes resulted in an 87 per cent 
retention of the orijinal ascorbic acid content of tomatoes. 
Holding oooked tomatoes on the steam table for 15 minutes 
caused no further loss in their ascorbic acid values. 

Shredded cabbage held at room temperature for one hour 
retained, in most of the samples studied, from 94 to 100 per 
cent of its original ascorblo acid content. Cabbage steamed 
for seven minutes showed 79 to 88 per cent retentions of as- 
corbic acid. Holding cooked cabbage on the steam table for 
15 minutes caused a slight decrease in its ascorbic acid value. 

The retention of the ascorbic acid in potatoes during 
oooking was about 86 per cent. Mashed potatoes showed a 55 
per cent retention of their original ascorbic acid oontent. 
Holding masliod potatoes on the back of the stove for 45 min- 
utes caused a considerable decrease. 

Haw spinach held on tho steam table for 15 minutes gave 
an ascorbic add retention of 82 per cent. Cut spinach held 
at room temperature lost its ascorbic acid rapidly. 



45 



The data indicated that during June and July of 1945 the 
ranges of asoorblo aold values In 100-gram amounts of some 
vegetables were as follows: 

Tomatoes, raw 14.9 - 20.2 mg. 

■ steamed 12.8 - 15.7 " 

" held on steam table 15 minutes . 11.7 - 17.9 " 

Cabbage, raw 55.2 - 54.2 

" steamed. 34.4 - 39.0 " 

" held on steam table 15 minutes . 33.0 - 30.1 " 

Potatoes, raw 2P.3 - 30.2 " 

mashed 17.7 - 21.7 ■ 

" " held on stove 45 minutes. . 13.2 - 17.1 " 

Spinach, raw 10.9 - 18.7 " 

n held on steam table 15 minutes. . 8.0 - 14.4 " 
" " at room temperature 60 minutes 8.5 - 12.6 " 
The findings in this study showed that commendable proce- 
dures were used in the preparation and serving of these vege- 
tables at the college cafeteria. 



46 



ACKNOWLEDGMENT 

Sincere appreciation is hereby expressed to Reverend 
Mother Thomas whoso encouragement prompted the undertaking 
of this work and to Rovorond Mother Cecilia and the Ursullne 
Sisters of Paola, Kansas, who made its completion possible. 

Deep gratitude is also due to Dr. Leah Asoham whose 
direction and guidance have been Invaluable and to Miss Mary 
Smull for her gracious oooperation in the cafeteria project. 



47 



LITERAT'If.E CITED 



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Vitamin C. In: The Vitamins. Chicago. Amer. Ked. Assoc. 
637 p. 1939. 

Bessey, 0. A. and C. 0. King. 

The distribution of vitamin C In plant and animal tissue 

and its determination. Jour. Biol. Chem. 103:687-698. 1933. 

Bray, H. G. and W. V. Thorpe. 

Sampling of cooked cabbage in nutrition surveys. Nature. 
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Brown, A. P. and F, Moser. 

Vitamin C content of tomatoes. Pood Res. 6:45-55. 1941. 

Burrell, R. C., H. D. Brown, and V. R. Ebrlght. 

Ascorbic acid content of cabbage as influenced by variety, 
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Currence, T. II. 

Comparison of tomato varieties for vitamin C content. 
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Curlar, K. L. , J. B. Jones, K. W. Harris, and P. Penton. 

Ascorbic acid, thiamin, and riboflavin retention in fresh 
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Daum, K. , M. Alnione, and S. Hollister. 

Ascorbic acid in institutional food. Jour. Amer. Dietet. 
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Dove, W. P., E. P. Murphy, and R. V. Akeley. 

Varietal differences and inheritance of vitamins C and A 
in potatoes. Genetics. 28:72. 1943. 

Dunker, C. and C. Fellers. 

Vitamin C content of spinach. Amer. Soc. Hort. Scl. Proc. 
36:500-504. 1938. 

Esselen, V« B., M. E. Lyons, and C. P.. Fellers. 

The composition and nutritive value of potatoes with special 
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1942. 

Gleim, E., M. Albury, K. Vlsnyei, J. R. McCartney, and P. Fenton. 
Th9 effect of quantity preparation procedures on vitamin re- 
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22:29-31. Jan. 1946. 



48 



Gould, S,, D. K. Tressler, and C. G. King. 

Vitamin C content of vegetables. V. Cabbage. Pood Res. 
1:427-433. 1956. 

Halllday, E. f and I. Noble. 

Recent research In foods. Jour. Home Econ. 20:15-21. 1936. 

Hallswork, E. 0. and V. M. Lewis. 

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1944. 

Hamner, K. C., l. Bernstein, and L. A. Maynard. 

The effects of light intensity, day length, temperature, and 
other environmental factors on ascorbic acid content of toma- 
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Higglns, Miriam JSason. 

The retention of ascorbic acid in institution and in home- 
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46 p. 1342. " 

Hlnaon, W. P., k. k. Brush, and E. G. Halllday. 

The nutritive value of canned foods: VI. Effect of large 
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Ijdo, J. B. h. 

Vitamin C content of different species of potatoes. Nutr. 
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Ireeon, M. 0. and M. S. Eheart. 

Ascorbic acid losses in cooked vegetables. Jour. Home Econ. 
36:160-155. 1944 

Isgur, B. and C. Fellers. 

A preliminary study of the relationship between vitamin C 
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1939. 

Jenkins, Q. N. 

Ascorbic acid in mashed potatoes. Nature. 151:473. 1943. 

Julen, C. 

The potato as a source of vitamin C. Nutr. Abs. and Rev. 
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Kahn, R. K. and E. G. Halllday. 

Asoc:bic acid content of white potatoes as affected by 
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Assoc. 20:220. April 1944. 



49 



Lsmpitt, L. H., L. C. Baker, and T. L. Parkinson. 

Disappearance of the ascorbic acid In raw cabbage after 
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Leichsenring, J. 

Factors affecting the nutritive value of potatoes. Progress 
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Hack, G. L. and D. K. Tressler. 

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Mayfield, H. L. and J. E. Richardson. 

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1940. 

McCay, C. M., M, Pijoan, and H. R. Taubken. 

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1944. 



50 



Procter, B. and D. Oreenlle. 

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Fyke, Magnus. 

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Pood Hes. 



Rangauathan, S. 

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51 



Streightoff, P., H. E. Munaell, Ben-Dor Ean-Aml, It. L. Orr, 
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